Various robotic vehicles have been developed in the past. To obtain maximum agility, such vehicles have incorporated an all-wheel drive dual-body design where the bodies are disposed parallel to each other with a transverse pivot, generally at their mid-point, disposed transversely to the direction of forward or rearward motion. For example, highly mobile tractors have been designed using such a transversely mounted mid-body pivot for independent rotation in the vertical plane of forward motion about such pivot between the two bodies of the vehicle. This design is illustrated in U.S. Pat. No. 1,430,251. More recently, in the field of lunar exploration rovers, Klarer in "A Highly Agile Ground Assessment Robot (HAGAR) for Military Battlefield and Support Missions", SAND94-0408C (1994), and in "R.A.T.L.E.R.: Robotic All Terrain Lunar Exploration Rovers", SAND92-1821C (1992), has revealed similar designs. The basic concept of the prior art designs is illustrated in FIG. 1 of this application. FIG. 1 is a section view through a pivot 10 which extends through bodies 12 and 14. Each of the bodies 12 and 14 has stationary bushings, such as 16, 18, 20, and 22. The bushings 16, 18, 20 and 22 fully surround the pivot 10 so that the bodies 12 and 14 can rotate in a plane perpendicular to the longitudinal axis of pivot 10.
There are numerous problems with this type of design. In order to run power or communication wiring from one of the bodies 12 to the other 14, or vice versa, slits or openings were needed to be made between the bushings in each of the bodies 12 and 14 for entrances and exits of such wires. Thus, for example, slits made to the pivot 10 between bushings 16 and 18 would weaken the pivot 10 in that location. Additionally, if maintenance work was necessary or additional wires had to be added and connectors were disposed on wiring inside the pivot 10 in area 24, such connectors would get hung up on the slits used for access for such wires to get through the pivot 10 in the first place. Another problem with the use of a pivot 10 which goes cleanly through both bodies 12 and 14 is that as shown in FIG. 1, it separates the bodies 12 and 14 into two halves where communication with wiring becomes problematic. The prior art design shown in FIG. 1 also had problems in designing an effective travel stop. Although one attempted design was to put a projection on the pivot 10 which would, within bodies 12 or 14, strike a fixed object, the problem was that the pivot 10 was of such a diameter so as to present a significant lever arm on the projection mounted to its outer surface. Thus, what resulted in the past was shear failures of the travel stop. The function of a travel stop is significant in this particular prior art design in view of the fact that a variety of wires for both power and signals cross through the area 24 from body 12 to 14 and vice versa. This means that if undue relative rotation between bodies 12 and 14 were to occur, some of those wires could be cut, causing a battery or other power system failure or even a fire.
Yet another problem with the prior designs which used carbon composite bushings, with an aluminum pivot 10 was that galvanic action created maintenance problems at the interface of those two components.
Accordingly, the apparatus of the present invention seeks to improve the prior art design revealed in FIG. 1 and present a comparable degree of agility to the vehicle, while at the same time providing the enhanced benefits of a more compact design which alleviates the problems previously described in the prior art design of FIG. 1. Just how such problems in the prior art design are overcome is best understood by a review of the preferred embodiment of the invention which appears below.